David Kirkpatrick

June 17, 2010

Quantum dot research may lead to dramatic solar efficiency increase

Filed under: Science — Tags: , , , , — David Kirkpatrick @ 11:47 pm

This seems like a week full of a lot of good solar efficiency news. As I’ve written many, many times (hit the solar link in the sidebar), solar power needs continued breakthroughs in two areas to become market-viable — costs must continue to come down and efficiency needs to continue to increase. This news out of UT Austin points toward potential very dramatic efficiency increases.

From the link:

Conventional solar cell efficiency could be increased from the current limit of 30 percent to more than 60 percent, suggests new research on semiconductor nanocrystals, or quantum dots, led by chemist Xiaoyang Zhu at The University of Texas at Austin.

Zhu and his colleagues report their results in this week’s Science.

The scientists have discovered a method to capture the higher energy sunlight that is lost as heat in conventional .

The maximum efficiency of the silicon solar cell in use today is about 31 percent. That’s because much of the energy from sunlight hitting a solar cell is too high to be turned into usable electricity. That energy, in the form of so-called “hot ,” is lost as heat.

If the higher energy sunlight, or more specifically the hot electrons, could be captured, solar-to-electric power conversion efficiency could be increased theoretically to as high as 66 percent.

If you prefer the raw feed, here’s the release the linked story is based on.

September 25, 2008

The latest news on graphene

Filed under: Science, Technology — Tags: , , — David Kirkpatrick @ 4:58 pm

I’ve done a lot of graphene blogging and here’s the latest on the atom-thick carbon nanomaterial.

The release:

New Graphene-Based Material Clarifies Graphite Oxide Chemistry

September 25, 2008

AUSTIN, Texas — A new “graphene-based” material that helps solve the structure of graphite oxide and could lead to other potential discoveries of the one-atom thick substance called graphene, which has applications in nanoelectronics, energy storage and production, and transportation such as airplanes and cars, has been created by researchers at The University of Texas at Austin.


To get an idea of the nanomaterial graphene, imagine a lightweight material having the strongest chemical bond in nature and, thus, exceptional mechanical properties. In addition it conducts heat better than any other material and has charge carriers moving through it at a significant fraction of the speed of light. Just an atom thick, graphene consists of a “chickenwire” (or honeycomb) bonding arrangement of carbon atoms—also known as a single layer of graphite.

Mechanical Engineering Professor Rod Ruoff and his co-authors have, for the first time, prepared carbon-13 labeled graphite. They did this by first making graphite that had every “normal” carbon atom having the isotope carbon-12, which is magnetically inactive, replaced with carbon-13, which is magnetically active. They then converted that to carbon-13 labeled graphite oxide and used solid-state nuclear magnetic resonance to discern the detailed chemical structure of graphite oxide.

The work by Ruoff’s team will appear in the Sept. 26 issue of the journal Science.

“As a result of our work published in Science, it will now be possible for scientists and engineers to create different types of graphene (by using carbon-13 labeled graphene as the starting material and doing further chemistry to it) and to study such graphene-based materials with solid-state nuclear magnetic resonance to obtain their detailed chemical structure,” Ruoff says. “This includes situations such as where the graphene is mixed with a polymer and chemically bonded at critical locations to make remarkable polymer matrix composites; or embedded in glass or ceramic materials; or used in nanoelectronic components; or mixed with an electrolyte to provide superior supercapacitor or battery performance. If we don’t know the chemistry in detail, we won’t be able to optimize properties.”

Graphene-based materials are a focus area of research at the university because they are expected to have applications for ultra-strong yet lightweight materials that could be used in automobiles and airplanes to improve fuel efficiency, the blades of wind turbines for improved generation of electrical power, as critical components in nanoelectronics that could have blazing speeds but very low power consumption, for electrical energy storage in batteries and supercapacitors to enable renewable energy production at a large scale and in transparent conductive films that will be used in solar cells and image display technology. In almost every application, sensitive chemical interactions with surrounding materials will play a central role in understanding and optimizing performance.

Ruoff and his team proved they had made such an isotopically labeled material from measurements by co-author Frank Stadermann of Washington University in St Louis. Stadermann used a special mass spectrometer typically used for measuring the isotope abundances of various elements that are in micrometeorites that have landed on Earth. Then, 100 percent carbon-13 labeled graphite was converted to 100 percent carbon-13 labeled graphite oxide, also a layered material but with some oxygen atoms attached to the graphene by chemical bonds.

Co-authors Yoshitaka Ishii and Medhat Shaibat of the University of Illinois-Chicago then used solid state nuclear magnetic resonance to help reveal the detailed chemical bonding network in graphite oxide. Ruoff says even though graphite oxide was first synthesized more than150 years ago the distribution of oxygen atoms has been debated even quite recently.

“The ability to control the isotopic labeling between carbon-12 and carbon-13 will lead to many other sorts of studies,” says Ruoff, who holds the Cockrell Family Regents Chair in Engineering #7.

He collaborates on other graphene projects with other university scientists and engineers such as Allan MacDonald (Departments of Physics and Astronomy), Sanjay Banerjee, Emanuel Tutuc and Bhagawan Sahu (Department of Electrical and Computer Engineering) and Gyeong Hwang (Department of Chemical Engineering), and some of these collaborations include industrial partners such as Texas Instruments, IBM and others.

Co-authors on the Science article include: Weiwei Cai, Richard Piner, Sungjin Park, Dongxing Yang, Aruna Velamakanni, Meryl Stoller and Jinho An (all of the Ruoff research group at The University of Texas at Austin); Sung Jin An, formerly of Pohang University of Science and Technology (POSTECH-Korea) and a visiting graduate student in the Ruoff group during the study; Dongmin Chen (Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences); Stadermann; and Ishii and Shaibat of the University of Illinois-Chicago.

A high-resolution photo of Ruoff is available. Learn more about Ruoff’s work.

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  • September 18, 2008

    Graphene to double capacity of ultracapacitors

    Filed under: Science, Technology — Tags: , , , , — David Kirkpatrick @ 10:47 am

    From KurzweilAI.net — Looks like our old (well, new but well covered at this point) friend, graphene, will double the capacity of electric storage ultracapacitors.

    New Carbon Material Shows Promise Of Storing Large Quantities Of Renewable Electrical Energy
    Science News, Sep. 17, 2008

    University of Texas at Austin researchers have developed graphene-based ultracapacitor cells that could double the capacity of ultracapacitors, used to store electrical charge.

    Read Original Article>>

    April 8, 2008

    Breaking the petawatt laser barrier

    Filed under: Science — Tags: , , , — David Kirkpatrick @ 2:25 am

    Yowza. In a release today the University of Texas announced the Texas Petawatt laser exceeded one petawatt of power on March 31.

    The release:

    Most powerful laser in the world fires up

    AUSTIN, Texas—The Texas Petawatt laser reached greater than one petawatt of laser power on Monday morning, March 31, making it the highest powered laser in the world, Todd Ditmire, a physicist at The University of Texas at Austin, said.

    The Texas Petawatt is the only operating petawatt laser in the United States.

    Ditmire says that when the laser is turned on, it has the power output of more than 2,000 times the output of all power plants in the United States. (A petawatt is one quadrillion watts.) The laser is brighter than sunlight on the surface of the sun, but it only lasts for an instant, a 10th of a trillionth of a second (0.0000000000001 second).

    Ditmire and his colleagues at the Texas Center for High-Intensity Laser Science will use the laser to create and study matter at some of the most extreme conditions in the universe, including gases at temperatures greater than those in the sun and solids at pressures of many billions of atmospheres.

    This will allow them to explore many astronomical phenomena in miniature. They will create mini-supernovas, tabletop stars and very high-density plasmas that mimic exotic stellar objects known as brown dwarfs.

    “We can learn about these large astronomical objects from tiny reactions in the lab because of the similarity of the mathematical equations that describe the events,” said Ditmire, director of the center.

    Such a powerful laser will also allow them to study advanced ideas for creating energy by controlled fusion.




    The Texas Petawatt was built with funding provided by the National Nuclear Security Administration, an agency within the U. S. Department of Energy.